One of those concerns is the 6 Gbps SATA III support for fast 6G SSDs.
But in fact, a 2009 or 2010 Mac Pro has at least one killer PCIe card solution already announced, the OWC PCIe solution. That solution will almost certainly be faster than internal drive bays, even with a new Mac Pro, because the PCIe solution gets the full PCIe bandwidth. And it will work in existing Mac Pro systems and leave the drive bays open for hard drives, e.g. four fast 3TB Hitachi 7K3000 drives. So in my view, a PCIe solution is the best possible way to go, with maximum performance and the ability to stuff in 12TB of hard drive storage as well.
I know of another PCIe solution coming, though I am not at liberty to say when or from what company, but it will provide similar PCIe-based functionality. So bottom line is that 6 Gbps SATA is not a reason by itself to defer purchasing a Mac Pro or getting an MPG Pro Workstation.
As for Thunderbolt, peripherals are not likely to appear before the fall, won’t be cheap, and it would be surprising if a Thunderbolt PCIe card did not also appear in that time frame. Besides, existing solutions can provide pro-grade external storage already.
Yes, a new Mac Pro might have other goodies, but so far the processors and motherboard have yet to appear that would enable a meaningful jump. Ideally, one buys at just the right part of the product cycle, but for professionals with work to do, the time to buy is when getting work done is impaired by an existing system.
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